The specific aims of this study are: (1) to identify abnormalities of lymphocyte function, activation, or cytokine production that may predict disease activity, complications, and response to therapy in pediatric Crohn's disease; (2) to evaluate in vitro the effects of pharmacologic agents on lymphocyte function in Crohn's disease. The investigators will examine lymphocyte function and inflammatory mediators in the peripheral blood of patients with Crohn's disease as well as in control patients and disease controls.